1. Field of the Invention
The invention relates to liquid-melt aliphatic dicarboxylic acids having 8 to 18 C atoms in the carbon skeleton.
2. Discussion of the Background
Aliphatic dicarboxylic acids are widely used in a variety of applications. For example, they can be used as a raw material for the preparation of polyamides. An inexpensive preparation of polyamides starts from molten diamine and dicarboxylic acid. In this process, the components are melted, mixed and subjected to polycondensation in the melt. In practice, the disadvantage of the process is that the dicarboxylic acid can be melted only immediately before use, since it discolors severely in the molten state during prolonged storage. This discoloration is then transferred to the condensed polyamide. Such a discolored product is not accepted by the market.
To overcome this problem, the polycondensation is instead carried out in the aqueous phase. This process requires that large amounts of water must be heated and evaporated off on an industrial scale. Accordingly, aqueous phase polycondensation is not economically advantageous.
It is consequently desirable to discover routes for carrying out the polycondensation in the melt.